The class of `CGI.escapeHTML` result

[nobu]

The class of CGI.escapeHTML result is not consistent for escaped/non-escaped cases.

require 'cgi/escape'
class S<String;end
p %w[a &].map {|c|[c, CGI.escapeHTML(S.new(c)).class]}.to_h #=> {"a"=>S, "&"=>String}

Probably, should be String always?